I've been working on a quad tree demo for some time and used this gentleman's code as a study to learn:

However my results for the island scene look like this:

I started following the base code loosely, but to try and get the rendering of the quadtree correct I adhered quite closely to the terrain files as I was being driven slowly crazy. Even now when I see very little difference between the sets of code there must be some faults.

The above is how I init my vertices values, with data being an image file holding the height values. The land mass itself renders fine if I render it as a whole block without a quadtree using an indexed VAO and GL_TRIANGLES.

The indices generating function of the terrain chunks if I go the alternative route, however, is as follows:

I fixed the big issues using a different approach found on the rastertek site, but thankyou for replying. However, now I have bizarre frustum culling issues where nearby quads are being culled. I'll post a separate thread for that.